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Questions

When we send emails to users, should we download the body of the email and send it in the email body? Or should we tell them to visit the portal?
- At the moment, the body of the email == the body of the message. And files are assumed to be stored as plain text.
Should notifications of this nature be implemented now or later?
- Also, if the affected entity has child entities, should those be included in the notification?
How should we tie Entities to users in terms of notifications?
- Ownership? << It might be this.
- Favorites? << It might be this.
- Permissions? << I don't think it's this.
- Something else? << It could be a completely new set of services, allowing users to enable/disable notification. (Could be initialized from Favorites and Owners.)

Objects

Name	DBO	Migration	DTO
MessageContent (Immutable after creation)	Primary key: ID Foreign key: CreatedBy (UserGroup) Foreign key: MessageBody (S3 File Handle ID) Etag CreatedOn	Backup via ID Note: Etag is required because MessageStatus is mutable.	Interface ID CreatedBy (principal ID) S3 File Handle ID CreatedOn
MessageToUser (Immutable after creation)	Foreign key: ID (MessageContent) Subject (nullable) Self foreign key: InReplyTo (ID) (nullable) Foreign key: InReplyToRootId Recursive foreign key to primary key	Secondary to MessageContent	Implements MessageContent Subject (string, optional) Set of recipient IDs inReplyTo (optional) inReplyToRoot (optional)
MessageRecipient (Immutable after creation)	Foreign key: ID (MessageContent) Foreign key: Recipient ID (UserGroup)	Secondary to MessageContent
MessageStatus	Foreign key: ID (MessageContent) Foreign key: Recipient ID (UserGroup) States: UNREAD, READ, ARCHIVED	Secondary to MessageContent	ID Recipient State
Comment (Immutable after creation)	Foreign key: ID (MessageContent) Target type (Enum ObjectType) Target ID TBD: references to other Comments in the conversation*	Secondary to MessageContent	Implements MessageContent Target type Target ID
MessagingSettings	Part of UserProfile Use existing services to support this	Secondary to UserGroup	Should email be sent? Should emailed messages be READ automatically? Other options (as necessary) Blacklist of blocked users
CommentVotes	Primary key: Message ID Up votes Down votes Is-comment-inappropriate votes	TBD	ID Up Down
MessageBundle			Bundles the MessageToUser and Message Status
MessageRecipientSet			Set of recipient IDs

'* per Marcel, Comments may have a more complex set of references/relationships than Messages to Users have. Rather than just 'inReplyTo', it might be that one Comment is an 'answer' to another comment which is a question. Further, the multiple answers to a question may have 'previous' references which order them.

Other TODOs

Throttle message input
- Max 10 creations per minute
- Max 50 recipients
When adding a new person to a conversation, the new person should get the whole history of the conversation
- Might be implemented by forwarding ALL the previous messages
- OR by concatenating all previous into one new message
Configure Amazon SES
- Automated proposal:
  - Reroute bounce and complaints to SNS
  - Have a worker subscribe to the topic via SQS
  - Have a worker disable emails to hard-bounced recipients
  - The worker may email a Google Group to notify us of anything it cannot handle
  - Also flip flags in settings for complaints
  - Store the bounce/complaint in a blob
Add methods to send messages according to templates
- Each individual Message should be stored in its final form.
- This design choice would change for very very large notification message volumes.
- Templates:
  - Password reset
  - Welcome
  - Delivery failure
  - Entity shared
  - Entity changed
  - TBD

Message sender (worker)

Extend ObjectType to include a "MESSAGE" type
Have DBOMessage extend ObservableEntity
Send a change message when a message is created
Subscribe worker to the repo-changes topic
Look for MESSAGE-CREATED changes to process
The worker should always check to see if a message has already been sent, so that messages do not get resent every time the stack changes.
Whenever the message sending worker encounters an error:
- Send the sender of the message a notification with the summary of delivery failures
- Add CloudWatch metrics to count delivery failures
- If the message cannot be sent to anyone, mark the sender as the receiver of the message so that it doesn't get reprocessed (i.e. after migration)
Process change of other ObjectTypes (i.e. ENTITY) for notifications
- Needs additional state: either a link between ObjectID/Type and messageContent or ObjectID/Type and UserID (to prevent messages from being resent everytime the stack blows away the change messages)

Services

Sorting & Pagination
- Sort by creation date
- Sort by subject
- Sort by recipient name

Method	URI	Body	Parameters	Return	Description	Permission
POST	/message	MessageToUser		MessageToUser	Sends a message. Note, message delivery permission is on a recipient-by-recipient basis, asynchronous to the message creation. Unauthorized delivery may result in silent failure or a bounce message (TBD).	Authenticated User Must be admin to send to AUTH_USERS Must have SEND_MESSAGE permission on team to send to team
GET	/message/inbox		Sorting + pagination	Paginated results<MessageBundle>	Gets all messages the authenticated user has received	Authenticated User
GET	/message/outbox		Sorting + pagination	Paginated results<MessageToUser>	Gets all messages the authenticated user has sent	Authenticated User
GET	/message/{id}			MessageToUser	Gets a specific message	Sender or Receiver
POST	/message/{id}/forward	MessageRecipientSet		MessageToUser	Forwards a message to other recipients. This is equivalent to getting a (visible) message and POST-ing it to /message with a different set of recipients	Sender or Receiver
GET	/message/{id}/conversation		Sorting + pagination	Paginated results<MessageToUser>	Gets messages belonging in the same thread as the message ID. The list is filtered according to the user's ID.	Sender or Receiver
POST	/message/{id}/conversation/forward	MessageRecipientSet			Adds the set of recipients to the conversation by marking each recipient as a receiver of each message within the conversation. Should each recipient be sent the messages (i.e. via email)? Or should a notification be sent instead?	Sender or Receiver
PUT	/message/status	MessageStatus			Marks a message as: READ UNREAD ARCHIVED	Receiver
GET	/message/{id}/file			(Redirect)	Checks to see if the user can read the message and then redirects to the actual URL of the file associated with the message	Sender or Receiver
POST	/entity/{id}/message	MessageToUser		MessageToUser	Sends a message to the creator or administrator of the given entity. This allows users to ask for permission to see restricted entities. Added per	Authenticated user
POST	/entity/{id}/comment	Comment		Comment	Method for commenting on an entity.	Authenticated user with SEND_MESSAGE permission on entity
GET	/entity/{id}/comment		Sorting + pagination	Paginated results<Comment>	Gets messages belonging to the thread tied to the entity.	Authenticated user with READ permission on entity